Smoking is known as a risk factor for cardiovascular diseases. Recently, the use of heated cigarettes, which are expected to be a less toxic, has increased in Japan. However, little is known about their direct effects on cardiomyocytes. In the present study, we compared the effects of heated and a combustible cigarette smoke extracts (CSEs) on the cell viability, contractile function and intracellular Ca²⁺ dynamics of freshly isolated or cultured rat cardiomyocytes. We used Ploom X (PX) and IQOS (IQ) as heated CSEs, and 1R6F (RF) as a combustible CSE. The cell viability (MTS) assay using cultured myocytes showed that the order of toxic effects was RF>IQ>PX. Functional analysis using the Cell Motion Imaging System showed that all types of 1% CSE reduced cardiomyocyte contractility with their impairing activity RF≒IQ>PX. Intracellular Ca²⁺ dynamics analysis showed that all types of 1% CSE decreased the Ca²⁺-transient amplitude, which may be the mechanism of reduced contractility. In addition, RF treatment induce Ca²⁺ leakage (possibly from sarcoplasmic reticulum), which may be the cause of the increased diastolic Ca²⁺ levels. Furthermore, the spontaneous beating rate of cultured cardiomyocytes was markedly reduced by RF. Taken together, these results indicate that heated cigarette extracts are also toxic to cell viability and contraction of cardiomyocytes. In addition, each CSE had different effects on intracellular Ca²⁺ dynamics, suggesting that mechanism of action is different.